I am currently using an 8bitdo Zero icade controller with the latest PPSSPP on ios 10.
It works almost perfectly, except for the X button (A on the controller).
The button appears to get stuck on frequently (as it appears fully pressed on the touch overlay even after releasing the button).
I feel like it has something to do with the fact that the buttons still works within the menus even when unbound (its works like a back button). It is the only button that does, and the only button that sticks. I have tested the controller on other things and it appears to work fine.